The present invention relates generally to redundant system diagnostic techniques and, more particularly, to a method and system for program execution integrity for a communication-based angle sensor.
Modern vehicles are increasingly equipped with sophisticated electronic control systems for achieving finer control. For example, “steer-by-wire” is one type of control system in which a conventional direct mechanical linkage between the input device (e.g., steering wheel or handwheel) and the output device (e.g., steered road wheel) is replaced with a system incorporating components such as electronic input sensors, control circuitry, and output actuators. In particular, a system such as steer-by-wire (as well as other types of steering systems) utilizes a steering wheel angle sensor input for the operation thereof.
As is the case with many systems utilizing steering wheel angle information, the components of (and data produced by) the system are designed to be robust (i.e., redundant) so as to be able to continue system operation or fail safe in the event of a failure of one or more of the components. One way to ensure the robustness of a system component, such as a steering wheel position sensor, is by providing redundant components and/or signals in the system. However, this solution may not necessarily be cost effective or practical, depending on the system/component involved. With other approaches to ensuring system robustness, the system itself may be designed to verify the accuracy of sensor inputs, as well as the program execution integrity (PEI) of processing algorithms associated with the system. Examples of PEI diagnostics can include, but are not necessarily limited to, checksums, micro COP faults, redundant ALU, and runtime memory checks.
There are several different technologies available for sensing the steering angle of a vehicle, one of which utilizes a communication-based sensor. This type of sensor operates by transmitting a steering wheel angle message on a vehicle communication bus, which in turn provides a means for each module coupled to the bus to receive and utilize the information as necessary. In other words, the output of a conventional communication-based sensor is an actual computed parameter that is directly utilized by the system(s) receiving such information, as opposed to “raw” sensor data that is thereafter processed by the requesting system to compute the particular parameter. Thus, a communication-based sensor typically includes components such as individual sensing elements, a microprocessor, a communication controller and transceiver to interface with a communication medium (e.g., a vehicle communications bus).
Unfortunately, not all communication-based sensors process the raw data with the same degree of rigorousness and verification. When a robustly designed system uses information sent by a communication-based sensor, the information generated by the sensor should also meet the PEI criteria, input verification criteria and diagnostic timing requirements as do the rest of the system components. Accordingly, it would be desirable to be able to improve the reliability of information generated by existing communication-based sensors to meet robust system design criteria.